Carbon Dioxide
The underappreciated gas. CO2 is produced by metabolism and exhaled as "waste"—but it's far more than garbage. CO2 is the primary driver of breathing rate, a key blood pH regulator, and essential for oxygen delivery to tissues (Bohr effect). Low CO2 from overbreathing causes vasoconstriction and reduces oxygen delivery. Many symptoms attributed to "not enough oxygen" are actually from too little CO2.
CO2 Functions
Breathing Trigger
Rising CO2, not falling O2, triggers breathing. Chemoreceptors detect. Primary driver.
pH Buffer
CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3-. Breathing adjusts pH rapidly. Kidneys slower.
Bohr Effect
CO2 helps hemoglobin release oxygen. Higher CO2 = better tissue O2 delivery.
Vasodilation
CO2 relaxes blood vessels. Improves blood flow. Low CO2 = vasoconstriction.
Cerebral Blood Flow
Brain vessels very sensitive to CO2. Low CO2 reduces brain blood flow 40%.
Smooth Muscle
Relaxes bronchi, gut. Low CO2 = bronchoconstriction. Asthma connection.
Low CO2 (Hypocapnia)
Overbreathing
Most common cause. Stress, anxiety, habit. Blows off too much CO2.
Symptoms
Dizziness, tingling, brain fog, anxiety, chest tightness. Feel like need more air.
Paradox
Feel breathless despite breathing fast. Less O2 delivered due to Bohr effect.
Vasoconstriction
Vessels tighten. Cold hands/feet. Reduced blood flow. Brain affected.
Alkalosis
Blood too alkaline. Calcium binding changes. Tetany possible.
Chronic Pattern
Many people chronically low. Habitual overbreathing. Constant low-grade symptoms.
Building CO2 Tolerance
Buteyko Method
Reduce breathing volume. Nose breathing. Breath holds. Increase tolerance.
Slow Breathing
5-6 breaths per minute. Allows CO2 to accumulate. Resets chemoreceptors.
Extended Exhale
Exhale longer than inhale. Retains more CO2. Activates parasympathetic.
Breath Hold Practice
After exhale, hold briefly. Increases tolerance. Start gentle.
Nasal Breathing
Naturally slows breathing. Creates back pressure. Maintains CO2 better.
BOLT Score
Body Oxygen Level Test. Measures CO2 tolerance. Goal is 40+ seconds.